Automatic choke adjustment



Oct. 31, 1961 J. T. w. MOSELEY 3,006,617

AUTOMATIC CHOKE ADJUSTMENT Filed March 20, 1958 3 Sheets-Sheet 1 Jmas Z "(W/051541 ATTORNEY 'Oct. 31, 1961 J. T. w. MOSELEY 3,

AUTOMATIC CHOKE ADJUSTMENT Filed March 20, 1958 3 Sheets-Sheet 2 INVENTOR.

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1951 J. T. w. MOSELEY 3,006,617

AUTOMATIC CHOKE ADJUSTMENT Filed March 20, 1958 I 3 Sheets-Sheet 3 INVENT OR.

.fmws ZWM'osasy United States Patent O 3,006,617 AUTOMATIC CHOKE ADJUSTMENT James T. W. Moseley, Grosse Pointe Park, Mich., as-

signor to Holley Carburetor Company, Van Dyke, Mich, a corporation of Michigan Filed Mar. 20, 1958, Ser. No. 722,758 13 Claims. (Cl. 261-39) This invention relates generally to carburetors or other fuel controls for internal combustion engines, and more particularly to means for automatically operating the choking mechanism normally provided therein.

Most carburetors of present design include a coil-type thermostatic bimetal for controlling the amount of choke opening according to temperature. They also include a manifold vacuum responsive piston for initially opening the choke a predetermined degree when the cold engine starts and becomes self-sustaining. These pistons generally have vacuum bypass means associated therewith, comprising slots or ports, which are opened or closed by the position of the piston in order to control the extent of movement of the piston.

Automatic choke systems of the above type have proved to be unsatisfactory because the porting arrangement is such that the piston moves the same amount, and therefore the choke valve opens the same degree, regardless of whether the ambient temperature is 75 F. or 30 F., for example. Because of this, the carburetors deliver a mixture which is either too lean or too rich, depending on their original calibrations and settings, during certain seasons of the year.

The invention as hereinafter disclosed is directly concerned with this problem.

Accordingly, an object of the invention is to provide means for varying the degree of initial choke opening once the engine starts; more specifically, the object is to provide means for automatically varying the degree of initial choke opening in accordance with the ambient temperature once the engine becomes self-sustaining.

Other objects and advantages of the invention will become apparent when reference is made to the specification and the accompanying drawings in which:

FIGURE 1 is a perspective view illustrating a carburetor embodying the invention.

FIGURE 2 is a fragmentary, perspective exploded view illustrating the details of construction of the lefthand portion of FIGURE 1.

FIGURE 3 is an enlarged fragmentary elevational view, with portions thereof cut away and in cross-section, taken in the plane of line 33 of FIGURE 2 and looking in the direction of the arrows. FIGURE 3 illustrates in greater detail the piston and associated elements shown by FIGURE 2, as they would be constructed to provide one embodiment of the invention.

FIGURE 4 is a view similar to FIGURE 3, but illustrating a modification of the invention.

FIGURE 5 is an enlarged fragmentary side elevational view, with portions thereof cut away and in cross-section, taken on the plane of line 55 of FIGURE 1 and looking in the direction of the arrows. FIGURE 5 illustrates still another modification of the invention.

FIGURE 6 is a fragmentary end elevational view, with portions thereof cut away and in cross-section, taken on the plane of line 66 of FIGURE 5.

Referring to the drawings in greater detail, FIGURE 1 illustrates a carburetor 10 having a throttle body 12, an air intake 14 with induction passages therethrough adapted to be controlled by a choke valve 16, which is operatively connected by means of arms 18 and 20 and link 22 to the automatic choke control 24.

FIGURE 2 illustrates a housing 26, suitably secured as by screws 28 to the carburetor 10 and having a cylin- 3,006,617 Patented Oct. 31, 1961 der 30 formed therein containing a piston 32 which is connected through a linkage 34 to the choke lever 36. A shaft 38, extending through and rotatable in one wall of the housing 26 has secured to it at one end thereof a choke lever 36, and at the other end thereof a lever 20 (FIGURE 1). The choke lever 36 has an outwardly extending projection 40 which is adapted to coact with the free outer end 42 of thermostatic element 44 through an arcuate opening 46 in the housing cover plate 48.

The thermostatic housing 50 has a centrally located shaft rigidly secured therein to which the inner end of the thermostatic element 44 is secured. Any suitable means such as the clamping ring 52 may be employed to hold the cover plate 48 and housing 50 in alignment with and against the housing 26. The ring 52 may be secured by means of screws 54 and the cooperating threaded portions 56.

Conduit 58 communicates between a source of heated air and the chamber formed by the cover plate 48 and housing 50. Its purpose is to deliver a controlled amount of air, which is at a temperature indicative of engine temperature, to the thermostatic element 44 in order that the element 44 may react to it and influence the position of the choke valve 16 accordingly. The path of this heated air is indicated by the arrows in FIG. 2, its ultimate exit being to the intake manifold through a porting means between the piston 32 and the walls of the cylinder 30; the latter is to be described more fully in connection with FIG. 3.

Conduit 60 communicates generally between the cylinder 30 and a source of engine manifold vacuum in such a manner as to cause movement of the piston 32 in a direction resulting in a clockwise rotation of lever 36, and at the same time to draw the heated air referred to above through conduit 58.

The construction described above is well known to those skilled in the art as the standard automatic choke employed on most carburetors. Other features such as a fast idle mechanism are normally associated therewith. but they need not be described since they form no part of the invention.

FIGURE 3 illustrates in greater detail the construction of -a choke vacuum piston 32 and cylinder 30 embodying the invention. The piston 32 has a generally cylindrical cavity 66 formed therein so as to be open at one end. The other end of the piston is closed and is subjected to manifold pressures, as described above. A temperature responsive bimetallic strip 68 is located within cavity 66 and may be secured to the piston 32 by means of slots 70, formed within the walls of cavity 66 and adapted to receive the ends of the thermostatic element. A bracket 78, which may extend through or about the thermostat 68, is secured at one end to the thermostat, as by plates and 82. The other end of the bracket 78 is pivotally connected through any suitable means such as pin 62 to a linkage 34, which in turn is pivotally secured to the choke lever 36 as by means of pin 64. The slots 72 which constitute the porting means already described above may be formed in the wall of cylinder 30.

FIGURE 4 illustrates a modification of the invention in which a thermostatic element is employed to vary the effect of piston movement by virtue of a cam arrangement. The piston 102 is pivotally connected to a linkage 104 by means of a pin 106; the opposite end of the link 104 has secured to it a pin 108. The choke lever 110, similar to lever 36 of FIGURE 3, has a slot 112 formed in the extending portion 114, which is adapted to slidably receive the pin 108.

The thermostatic element 100 is operatively connected to link 104 as by pin 108 while its other end is anchored toportion 1140f choke lever 110, by means of pin 116.

Orifice 74, as in FI GURES2 and 3, opens into the cylinder 3!] and communicates with conduit 76 leading .to a source of engine manifold vacuum.

In FIGURE 5, which illustrates a second modification of the invention, a thermostatic bimetal 118 has one of its endssuitably secured to the choke shaft120, as by pin 122, at a point exterior of and adjacent to the air intake 14. The thermostat 118 is'located between the intake 14 and a member124 which ispivotally mounted on and about the chokeshaft 120. The'other end of thethermostatissecured to the member 124 by any suitable means such as 'pin12'6. A second' member, arm 128, is rigidly mounted to the=choke shaft 120 on the opposite side of the-member 124 as -is thermostat 118. The arm 128'has"an'elongated slot 130 adapted-to slidably receive'the'laterallyextending'end 131 ofthe choke linkage 22, at one end thereof and extending in 'a'substantially radial direction fromthe chokeshaft 120.

The member 124 is formed to provide a generally arcuate' slot 132 of relatively uniform width-slightly greater than the diameter of end 131 of linkage 22. The slot 132is constructed s'o asto have'each point thereon at an increasingly greater distance'awa'y from the center of the choke shaft 120. The end of'slot 132 which'is at the greatest distance away from shaft 120 is in line with the extreme end of slot 130'while the other end'ofslot 132 is in line with the closer end of .slot 130 when member 124 is suitably rotated with respect to arm'1 28.

Operation of invention Assuming for the purpose ofillustration, that the-engine is cold and is being cranked, the thermostatic element 44' will bein its unwound condition, thereby causing its end 42'to'position projection-40 of lever 36in its extremecounter-clockwise position. The lever 36,- being secured to shaft =38'rotatesth'e shaft and arm 20 which is secured to 'it'counter-cloc-kwise to cause the choke valve 16 to assume a position which substantially closes' off the fiowof air throughthe carburetor induction passage 14. All of these elementswill-continue' to occupy these respective positions wh ile tlie engine" isbeing cranked.

As 'soon as the en'gin'e fires and becom'es:self sustaining,

manifold vacuum rises to a value suflicie'nt to'move the vacuum piston 32 downwardly in opposition to the-' force of the'rniostat '445 frhe extent of -move'ment For this piston is determined by the position of the porting :means, that-is,- slet's"72 within the cylinder'30:

'As' sobn as th'e p'i'stdn' 32 1incove'r's"the ends of'the slots the effect or the niannemwaeuum: i s reduced' to such a degreethat the pistonis unable to further: overcome theopposingrforceof the thermostat44'. -AS the engine continues to run, 5 air" is drawn from any suitable -stove ('noP'shdWnTthroUgh conduits58, 88and90, through an orifice- 92 in coverplate- 48,.and intothe chamber formed 'by'thehousing' -SD-'and-cover-plate 48. This air warms the thermostat-44 and passes-throughthe arcuate opening '46-within'thecover-plate. The'air is then drawn through the slots 72incylinder 30, Ultimately, the air is drawn through-orifice 'idinto'conduit 76 leading from the cylinder30'to conduits 98 and 60, which'are in turn connected 7 to a source-of manifold vacuum.

From the foregoinggit is-evident that as-soon as the engine-starts to runthe'vacuum piston 32, by virtue of its movement, causesthe choke valve- 16 to open some desired and predetermined amount. However, the amount of this opening, in order thatoptimum operating characteristics can be achieved. should be varied in accordance with the ambient temperature, That is, if the ambient temperature were-0 P the choke should possibly be-openedonly five degreesyon the other hand, if the ambient temperature were 65 F., the choke might have to-be openedfifteen degrees. The above stated temperatures and associated degrees of initial opening of the choke'valve are not intendedto-be accurate, but to merely illustrate the problems. These variations of initial choke opening are necessary in order to deliver a richer fuelair ratio when the ambient temperature is relatively low.

The above described variations are made possible with the use of the invention. The thermostats 68, and 118, by virtue of their positions, are responsive to ambient temperatures; accordingly they vary as that temperature changes.

The thermostat 68, as illustrated in FIGURE 3, will cause the bracket 78'to move towards the closed end of piston 32 as theambient temperature increases, and vice versa. This in turn causes the distance between pin 64 and-the end 84 of piston 32 to shorten as'the'temperature increases and lengthen as the temperature decreases. Therefore, it becomes evident that as this distance becomes greater due to a relatively low ambient temperature'and the piston moves to a point whereby the end 84 uncovers the slots 72, the degree of choke opening is less than if the distance were shorter, as would be the case when ambient temperature is higher. This operation provides a variable fuel-air mixture dependent on the ambient temperature. a

The modification as disclosed in FIGURE 4 operates in the same general manner. However, the shortening and lengthening operation described above is performed by the thermostat 100 and a cooperating pin and cam arrangement. In this embodiment, as the ambient temperature decreases, the thermostat I'Otltends to wind, thereby pulling the pin 108 and attached link 104 downwardly from the position illustrated through the cam-type slot 112. This in turn causesthe distance between any point on portion 114 and end 86 of piston 102 to increase, again decreasing the degree of initial choke opening. The opposite operation takes place when ambient temperature increases.

The modification disclosed in FIGURES 5 and 6 is different from the previous embodiments in that the correction due to ambient temperature takes place at a point where the linkage 22 is connected to the choke valve arm 18 (FIGURE 1).

In this modification, as the ambient temperature becomes relatively low, the thermostatic coil 118 tends to wind and cause member 124, through pin 126, to rotate ina clockwise direction about the choke shaft 120. The end of link 22 extending through slots 130 and 132 is thereby caused'to'move outwardly within slot 130 due to the cam action of slot 132 in member 124; the member 124 does not move because it is rigidly secured to the choke shaft 120. It therefore becomes evident that when the vacuum piston 32 moves its predetermined amount, as determined by the slots 72, a fixed and constant movement will be imported to link 22. However, since the link 22 is now at a point which is farther away from the center of rotation of choke shaft and arm 128, this fixed initial movement of link 22 will cause a lesser angular movement of arm 128 and a lesser degree of opening ofchok e valve 16. Of course, the converse is true; that is, as the ambient temperature increases, the link .22 will tend to move toward the center of rotation of arm 128 and cause a greater degree of initial choke opening.

From the foregoing, it will be apparent that superior regulation of the choke valve will be obtained because the'correct amount of initial choke opening is: regulated in accordance with ambient temperature.

Other modifications of the invention may be made without exceeding the scope of the invention, as defined by the appended claims.

What I claim as my invention is:

1. In a carburetor for an internal combustion engine, a choke valve, a source of suction related to engine operation, temperature responsive means influencing the position of said choke valve,.-pressure responsive means communicating with said source of suction and being operatively connected to move said choke valve, and

second temperature responsive means for'increasing'the 7 amount of choke movement due to said pressure responsive means in accordance with increase in temperature without restricting the operativeness of said pressure responsive means.

2. In a carburetor for an internal combustion engine, a choke valve, temperature responsive means influencing the position of said choke valve, a source of suction available upon starting of said engine, pressure responsive means including a cylinder and piston therein communicating with said source of suction, said piston being positioned in response to said suction and being operatively connected to said choke valve, and additional temperature responsive means connecting said choke valve to said piston for varying the position of said piston prior to the starting of said engine so as to increase choke opening movement with increase of temperature and decrease choke opening movement with a decrease of temperature upon starting of said engine.

3. In a carburetor for an internal combustion engine, a choke valve, temperature responsive means influencing the position of said choke valve, a source of engine manifold suction, pressure responsive means including a cylinder and piston therein communicating with said source of suction and being operatively connected to said choke valve, and additional means for varying the position of said piston with respect to said choke valve when said choke valve has reached a closed or more nearly closed position, said means allowing said piston to move to a predetermined point when subjected to engine manifold suction.

4. In a carburetor for an internal combustion engine, having an offset choke valve mounted therein, an automatic choke control device, said device comprising a thermostatic control for said choke valve, means responsive to engine suction for moving said choke valve in the opening direction upon engine starting, and means for changing a fixed movement of said suction responsive means to a variable movement of said choke valve.

5. In a carburetor for an internal combustion engine having a choke valve mounted therein, an automatic choke control device, said device comprising a thermostatic control for said choke valve, suction responsive means operative to move said choke valve in the opening direction when the engine starts, and automatic temperature responsive means interposed between said suction responsive means and said choke valve for changing a fixed movement of said suction responsive means to a variable movement of said choke valve.

6. In a carburetor for internal combustion engines, an offset choke valve, means including a heat responsive device to move said choke valve in a closing direction at low temperature, a device responsive to engine suction and including a cylinder and a piston therein operatively connected to said choke valve for causing a partial opening of said choke valve against the tension of said thermostat upon starting of the engine, suction bypass means associated with said cylinder for limiting the stroke of said piston, and means for varying the efiective length of said piston stroke on said choke valve.

7. In a carburetor for an internal combustion engine having an ofiset choke valve mounted therein, an automatic choke device comprising a thermostatic control for said choke valve, suction responsive means operative when the engine starts to move said choke valve in the opening direction, and means including a thermostatically controlled cam for changing a fixed movement of said suction responsive means to a variable movement of said choke valve.

8. In a carburetor for an internal combustion engine, a choke valve, temperature responsive means influencing the position of said choke valve, a source of suction available upon engine starting, pressure responsive means comprising a cylinder and piston therein communicating with the source of suction and operatively connected to said choke valve, and additional means including a thermostatically controlled cam operatively connected between said choke valve and said piston for varying the position of said piston prior to engine starting.

9. In a carburetor for an internal combustion engine, a choke shaft, a choke valve mounted on and rotatable with said shaft, temperature responsive means influencing the position of said choke valve, a source of engine suction, pressure responsive means comprising a cylinder and piston therein communicating with said source of suction and operatively connected to said choke valve, and additional means including a thermostat mounted on said choke shaft for controlling the position of said piston independently of said engine suction.

10. In a carburetor for an internal combustion engine having a choke valve therein, an automatic choke control device, said device comprising a choke shaft secured to said valve, a member secured to said shaft and adapted to be rotated therewith, a housing, a second shaft mounted through one side of said housing and adapted to be rotated therein, an arm secured to one end of said second shaft externally of said housing so as to be rotatable therewith, means connecting said member with said arm, a cylinder open at one end and substantially closed at its other end, a piston in said cylinder, 2. second arm having a projection thereon secured to the other end of said second shaft within said housing and adapted to rotate said second shaft, conduit means leading from the space between the said piston and the closed end of said cylinder and communicating with a source of engine suction, second conduit means leading from the said housing and communicating with a source of heated air at substantially atmospheric pressure, thermostatic means within said housing adapted to bias said projection in a direction so as to close said choke valve, and connecting means including a thermostatically controlled cam therein between said second arm and said piston enabling said piston to variably oppose the movement of said thermostat whenever said engine is running.

11. In a carburetor for an internal combustion engine having a choke valve therein, an automatic choke control device comprising, a choke shaft secured to said valve, a first member secured to said shaft and adapted to be rotated therewith, a second member secured to said shaft and adapted to be rotated thereabout, a housing, a second shaft mounted through one side of said housing and adapted to be rotated therein, an arm secured to one end of said second shaft externally of said housing so as to be rotatable therewith, means connecting said first and second members with said arm, a cylinder open at one end and substantially closed at its other end, a piston in said cylinder, a second arm having a projection thereon secured to the other end of said second shaft within said housing and being adapted to rotate said second shaft, conduit means leading from the space between the said piston and the closed end of said cylinder and communicating with a source of engine suction, second conduit means leading from the said housing and communicating with a source of heated air at substantially atmospheric pressure, thermostatic means within said housing adapted to bias said projection in a direction so as to close said choke valve, connecting means between said second arm and said piston enabling said piston to oppose the movement of said thermostat whenever said engine is running, and a second thermostat secured to said choke shaft and adapted to rotate said second member with respect to said first member in a manner so as to vary the efiect of said piston on said choke valve in accordance with temperature.

12. In a carburetor for an internal combustion engine having a choke valve therein, an automatic choke control device comprising, a choke shaft secured to said valve, a member secured to said shaft and adapted to be rotated therewith, a housing, a second shaft mounted through one side of said housing and adapted to be rotated therein, an arm secured to one end of said second shaft externally of said housing so as to be rotatable therewith, means conend and substantially closed at its other-end, a piston in saidtcylinder, a second arm having'a projectiontthereon secured tothe other end of said second shaft within .said housing and being adapted to rotate said secondrshaft, conduit means leading from thespace-between the said piston and the closedend of said cylinder and communicatingtwith a source of engine suction, second conduit means leading from the said housing and communicating with a source of heated air at substantially atmospheric pressure, thermostatic means within said housing adapted to bias said projection in a direction so-as to close said choke valve, and connectingmeans'of thermostatically determined length between said second arm and said piston enabling said piston to variablyoppose the movementof said thermostat whenever said engine is running.

13. In a carburetor for an internal combustion engine having. a choke valve therein, an automatic choke control device comprising,a choke. shaft secured to said valve, a member secured to said shaftand adapted to be rotated therewith, a housing, a second shaft mounted'through one side of said housing. and adapted to be -rotated therein, an arm'secured to one end of said second Sshaftexternally of said housing so asto be'rotatable therewith, means con- 2 meeting said member, with saidzarm, a source of engine suction, a cylinder open at one end and substantially closed at its other. end having engine suction bypass means formed therein, a piston in said cylinder responsive to said engine suction and adapted to at times control and at other times be controlled by said bypass means, a second arm having a projection thereon secured to the other end of said second shaft Within said housing adapted to rotate said second shaft, conduit means leading from the space between the said piston and the closed end of said cylinder and communicating with said source of engine suction, second conduit means leading fromthe said housing and communicating with a source of heated air at substantially atmospheric pressure, thermostatic means within said housing adapted to bias said projection in a direction'so as to close said choke valve, and connecting means including a thermostatically controlled link between said second arm and said piston enabling said piston to have a variable total stroke and yet be controlled by said bypass means so as to oppose themovement of said thermostat wheneversaid engine is running.

References Cited in the file of this patent UNITED STATES PATENTS 2,609,806 Winkler Sept. 9, 1952 2,694,559 Gordon et al Nov; 16, 1954 2,698,168 OlSOn Dec. 28, 1954 

